ESBL-producing Klebsiella Pneumoniae isolated from dairy cows with pneumonia: insight into their epidemiology, genetic features and antimicrobial resistance profiles.

Klebsiella pneumoniae is a common cause of respiratory tract infections in humans and animals. This study surveyed the epidemiology and analyzed the genetic and resistance characteristics, and the pathogenicity of 37 K. pneumoniae from 316 dairy cows with pneumonia in Hebei Province (north China). To clarify the relationship between the isolates, antimicrobial susceptibility testing, PCR, high viscosity, extracellular polysaccharide content, biofilm formation and mouse infection model were used to decipher the relationship between different phenotypes of strains and drug resistance and virulence. Whole-genome sequencing was used to analyze and characterize the genetic features of some strains. Clinical treatment with medication based on drug susceptibility results. According to the results of Vitek 2 compact and the broth microdilution test, there were 81.0 % (30/37) ESBL-producing K. pneumoniae with a higher multiple antibiotic resistance (MAR) index. The isolates were mainly resistant to β-lactam and aminoglycoside antibiotics. The most frequently identified beta-lactamase genes were bla, bla and bla, aph(3″)-Ib, aph(6)-Id, and aph(3')-Ia. IncFII(K), IncQ1, IncFIB(K), and repB (R1701) were the main resistant plasmid replicons identified and multiple-replicon plasmids often carried more drug resistance genes. The major clone was ST43. The phylogenetic analysis presented the genetic diversity and close phylogenetic relationship between strains from humans, economic animals, and the environment. Moreover, using a mouse infection model, this study demonstrated that isolates with certain virulence profiles and significant resistance characteristics exhibited higher infection levels. Clinical data analysis suggested that co-medication had a positive effect on the outcome of the treatment. This work indicated that strengthening the clinical attention and epidemiological monitoring of multidrug-resistant ESBL-producing isolates from different sources is necessary and urgent. This work indicated that it is urgent and necessary to enhance the clinical vigilance and epidemiological monitoring of multidrug-resistant ESBL-producing K. pneumoniae.